The present invention concerns a method of controlling a dual fuel engine.
Engines of the general kind set forth can be operated in a pure diesel or heavy oil mode or in a so-called dual fuel mode in which the prevailing kind of fuel is a gas, and diesel or heavy oil is used only for supporting ignition. An internal combustion engine of that kind is to be found in U.S. Pat. No. 8,671,911 B2.
That publication provides the arrangement of a knock sensor, by which the occurrence of knock can be detected. Depending on the detection signal a control unit can control the amount of gaseous and liquid fuel to the combustion chambers of the internal combustion engine.
A disadvantage in the state of the art is that retard ignition is necessarily provided as a reaction to the detection of a knock. That control strategy does not take account of the fact that knock can occur for various reasons and it is therefore not always expedient. In many cases, therefore, it may be necessary to take additional measures, as is also described in U.S. Pat. No. 8,671,911 B2 (reduction in the amount of gas introduced).